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1. Description of Related Art
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2. Field of the Invention
The present invention relates to mobile communications systems, and more specifically, to recovery of a gateway location register from a fault.
FIG. 1 illustrates a wireless communication system in accordance with the Global System for Mobile communication (GSM) standard. The GSM standard is designed to provide a uniform interface which allows mobile communication subscribers of various countries to operate their mobile devices regardless of the current location of the mobile subscriber. A mobile subscriber typically has a subscription with a network which is designated as the mobile subscriber""s home public land mobile network 110 (HPLMN). The HPLMN 110 has a home location register (HLR) 115 which contains, among other things, various information regarding the services provided to the mobile subscriber. When a mobile subscriber roams into a different network, which is referred to as a visited public land mobile network 120 (VPLMN), the VPLMN requires certain data regarding the mobile subscriber""s subscription. The data regarding the mobile subscribers subscription is also known as the mobile subscriber""s profile. The mobile subscriber""s profile is transferred from the HLR to a visitor location register (VLR) in the VPLMN 120.
In a GSM system mobile subscriber data is stored within the VLR that is associated with the mobile services switching center (MSC) that currently serves the mobile subscriber in order to reduce internetwork signaling between VLRs and HLRs. The decentralization of the VLRs within a GSM system (i.e., each MSC being equipped with a VLR) reduces internetwork signaling as well. So, for example, if the mobile subscriber is roaming in an area of the VPLMN 120 which is controlled by the MSC/VLR 130, the HLR 115 will transfer the mobile subscriber""s profile to MSC/VLR 130. Similarly, if the mobile subscriber is roaming in an area controlled by MSC/VLR 135, the HLR 115 will transfer the mobile subscriber""s profile to MSC/VLR 135. Although FIG. 1 illustrates the MSC/VLR as a single network node, one skilled in the art will recognize that the MSC and VLR can be implemented as separate network elements.
To increase the compatibility of GSM with other types of systems, it is anticipated that future versions of the GSM standard, also called Universal Mobile Telecommunications System (UMTS) will incorporate elements of other mobile communications systems. For example, the Japanese Personal Digital Cellular (PDC) system includes a network node which is used to reduce internetwork signaling known as a gateway location register (GLR). FIG. 2 illustrates an exemplary mobile communications system in accordance with the PDC system. Like a GSM system, a home network 210 includes an HLR 215 which contains the mobile subscriber""s profile. When a mobile subscriber roams into a visited network 220 the mobile subscriber""s profile is transferred to GLR 225. In GSM terms, the GLR can be described as a VLR for all mobile subscribers roaming from other networks. Hence, only one GLR is needed in each network.
FIG. 3 illustrates an exemplary UMTS system which incorporates the GLR of the PDC system. When a mobile subscriber of HPLMN 310 roams into VPLMN 320, the HLR 315 will transfer the mobile subscriber""s profile to GLR 325. Then, depending upon which area within the VPLMN 320 the mobile subscriber is roaming, the GLR 325 will transfer the mobile subscriber""s profile to the respective MSCNLR 330, 335 or 340. The introduction of the GLR 325 into a GSM/UMTS system reduces internetwork signaling because once the mobile subscriber roams into VPLMN 320, the HLR will only need to transfer the mobile subscriber""s profile to GLR 325. GLR 325 will be responsible for transferring the mobile subscriber""s profile to the proper MSC/VLR within VPLMN 320 as the mobile subscriber travels around the VPLMN 320.
The protocol used by GSM/UMTS systems for transferring data between VLRs and HLRs is the mobile applications part (MAP). Since GLRs are optional elements within the UMTS system, MAP procedures must be completely independent of the presence or absence of GLRs in a network. Accordingly, by using an HLR interface towards the VLRs and a VLR interface towards the HLRs, the GLR should be completely transparent. However, because of the dual nature of the GLR in the network it may be difficult for the GLR to behave in a way which simultaneously will be perceived as VLR behavior by the HLRs, and as HLR behavior by the VLRs. One such case is the fault recovery behavior of the GLR.
FIG. 4 illustrates a conventional method in a GSM system when an HLR is recovering from a fault. In step 405 the HLR loads the contents of its non-volatile backup memory into its dynamic memory. Next the HLR sends a MAP_RESET message to the VLRs to which the HLR""s subscribers are currently associated as indicated by the information in the backup memory in accordance with step 410. The MAP_RESET message triggers the VLRs to initiate a location update procedure towards the HLR at the next authenticated radio contact with a concerned mobile subscriber. Accordingly, in step 415 the VLR waits for an authenticated radio contact from the concerned mobile subscriber. In step 420 the VLR determines whether it has received an authenticated radio contact from the concerned mobile subscriber. If the VLR has not received an authenticated radio contact from the concerned mobile subscriber, in accordance with the xe2x80x9cNoxe2x80x9d path out of decision step 420, the VLR continues to wait in accordance with step 415. If the VLR receives an authenticated radio contact from the concerned mobile subscriber the VLR sends a MAP_UPDATE_LOCATION message to the HLR indicating that the VLR is serving the concerned subscriber in accordance with step 425. The location updates sent from the VLRs to the HLR will gradually restore and confirm the subscriber data of the restarted HLR.
FIG. 5 illustrates a conventional method in a GSM system when a VLR is recovering from a fault. In step 505 the VLR, which does not have a non-volatile backup memory for its dynamic subscriber data, deletes all IMSI records which remain in its dynamic memory. In step 510 the VLR waits for contact from either a mobile subscriber or from the HLR associated with a mobile subscriber. In step 515, the VLR determines whether it has received a location update request from a mobile subscriber. If the VLR receives a location update request from a mobile subscriber, in accordance with the xe2x80x9cYesxe2x80x9d path out of decision step 515, the VLR initiates the MAP_UPDATE_LOCATION procedure with the HLR associated with the mobile subscriber in accordance with step 520. The MAP_UPDATE_LOCATION procedure is used to send data associated with a mobile subscriber from an HLR to a VLR. Specifically, this data is sent in the framed MAP_INSERT_SUBSCRIBER_DATA indication message.
If the VLR has not received a location update request from a mobile subscriber, in accordance with the xe2x80x9cNoxe2x80x9d path out of decision step 515, the VLR determines whether it has received a roaming number request from an HLR in accordance with step 525. If a VLR has not received a roaming number request from an HLR, in accordance with the xe2x80x9cNoxe2x80x9d path out of decision step 525, then the VLR continues to wait for a contact from either a mobile subscriber or from an HLR in accordance with step 510. If the VLR has received a request for roaming number from an HLR, in accordance with the xe2x80x9cYesxe2x80x9d path out of decision step 525, then the VLR sends a MAP_RESTORE_DATA message, including an indication of the concerned subscriber whose data is being restored, to the HLR indicating that the VLR has experienced a fault in accordance with step 530. In response to the MAP_RESTORE_DATA message the HLR initiates the framed MAP_INSERT_SUBSCRIBER_DATA procedure with the VLR to provide subscriber data to the VLR in accordance with step 535.
Due to the GLR""s role in the network there is currently no provision for satisfying both the specified HLR behavior and VLR behavior during fault recovery. For example, the specified HLR fault recovery behavior requires that the GLR include a non-volatile memory for restoring backup data. However, GLRs may not have a non-volatile backup memory. In addition, the specified VLR fault recovery behavior requires that when a MAP_PROVIDE_ROAMING_NUMBER request message is received from the HLR, the GLR must unambiguously know to which VLR to forward the request to. However, since the GLR has lost its data due to the fault, the GLR will not know which VLR is currently supporting the mobile subscriber. Further, even assuming that the GLR has a non-volatile backup memory, the data stored in the non-volatile backup memory may be inaccurate, as a mobile subscriber may have moved to an area supported by another VLR since the last time the GLR has performed a backup. On the other hand, in a network without a GLR, a fault recovering VLR receiving a MAP_PROVIDE_ROAMING_NUMBER request message does not have this problem, since it does not have to forward the message. The fault recovering VLR assumes that since the HLR sent the MAP_PROVIDE_ROAMING_NUMBER to it, the indicated mobile subscriber is located in the service area of the fault recovering VLR. Consequently, the mobile subscriber""s profile should be restored from the HLR.
Accordingly, it would be desirable to provide methods and apparatus for GLR fault recovery in a UMTS system. Further, it would be desirable for the GLR fault recovery to be performed without violating the MAP protocol, i.e. using the specified message formats and not violating any specified message sequences.
According to exemplary embodiments of the present invention, methods and apparatus are provided for recovering from a fault in a radio communications network which includes a visitor location register and a gateway location register. A reset message is sent from the gateway location register to all visitor location registers associated with the gateway location register. A location update request is received by the gateway location register from one of the visitor location registers associated with the gateway location register. A location of a mobile subscriber is updated in the gateway location register in accordance with a location indicated in the location update message.
In accordance with another aspect of the present invention a roaming number request for a mobile subscriber is received by the gateway location register from a home location register associated with the mobile subscriber. The roaming number request is forwarded from the gateway location register to all visitor location registers associated with the gateway location register. A roaming number is received by the gateway location register from a visitor location register which is serving the mobile subscriber.
In accordance with this aspect of the present invention a restore data request message can be received by the gateway location register from visitor location registers which are not serving the mobile subscriber. A restore data response message can be sent from the gateway location register to the visitor location registers which are not serving the mobile subscriber, the restore data response message contains an error indication.
In accordance with yet another aspect of the present invention data from a backup memory is loaded in the gateway location register. A roaming number request for a mobile subscriber is received by the gateway location register from a home location register associated with the mobile subscriber. The roaming number request is forwarded from the gateway location register to a visitor location register, wherein the data loaded from the backup memory indicates that the visitor location register is serving the mobile subscriber.
In accordance with this aspect of the present invention a roaming number can be received by the gateway location register from the visitor location register which is serving the mobile subscriber. The roaming number can be forwarded by the gateway location register to the home location associated with the mobile subscriber.
Further in accordance with this aspect of the present invention a message indicating that the mobile subscriber is not being served by the visitor location register can be received by the gateway location register. A reset message can be sent by the gateway location register to all visitor location registers associated with the gateway location register other than the visitor location register from which the gateway location register received the message indicating that the mobile subscriber is not being served.
In accordance with a further aspect of the present invention a reset message is sent from the gateway location register to all visitor location registers associated with the gateway location register. The gateway location register waits for a location update message from a visitor location register which indicates that the subscriber indicated in the location update message is being served by the visitor location register.
In accordance with this aspect of the present invention the gateway location register can receive from a home location register a roaming number request for a mobile subscriber associated with the home location register. The gateway location register can send a roaming number response message to the home location register, wherein the roaming number response message includes an error indication.